hwmon: Add support for ltc2947

The ltc2947 is a high precision power and energy monitor with an
internal sense resistor supporting up to +/- 30A. Three internal no
Latency ADCs ensure accurate measurement of voltage and current, while
high-bandwidth analog multiplication of voltage and current provides
accurate power measurement in a wide range of applications. Internal or
external clocking options enable precise charge and energy measurements.

Signed-off-by: Nuno Sá <nuno.sa@analog.com>
Link: https://lore.kernel.org/r/20191021154115.319073-1-nuno.sa@analog.com
[groeck: Removed unnecessary checks when reading temperature and energy;
	 PAGE{0,1} -> LTC2947_PAGE_{0,1}]
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

Documentation/hwmon/index.rst

@@ -90,6 +90,7 @@ Hardware Monitoring Kernel Drivers
    lm95245
    lochnagar
    ltc2945
+   ltc2947
    ltc2978
    ltc2990
    ltc3815

Documentation/hwmon/ltc2947.rst

@@ -0,0 +1,100 @@
+Kernel drivers ltc2947-i2c and ltc2947-spi
+==========================================
+
+Supported chips:
+
+  * Analog Devices LTC2947
+
+    Prefix: 'ltc2947'
+
+    Addresses scanned: -
+
+    Datasheet:
+
+        https://www.analog.com/media/en/technical-documentation/data-sheets/LTC2947.pdf
+
+Author: Nuno Sá <nuno.sa@analog.com>
+
+Description
+___________
+
+The LTC2947 is a high precision power and energy monitor that measures current,
+voltage, power, temperature, charge and energy. The device supports both SPI
+and I2C depending on the chip configuration.
+The device also measures accumulated quantities as energy. It has two banks of
+register's to read/set energy related values. These banks can be configured
+independently to have setups like: energy1 accumulates always and enrgy2 only
+accumulates if current is positive (to check battery charging efficiency for
+example). The device also supports a GPIO pin that can be configured as output
+to control a fan as a function of measured temperature. Then, the GPIO becomes
+active as soon as a temperature reading is higher than a defined threshold. The
+temp2 channel is used to control this thresholds and to read the respective
+alarms.
+
+Sysfs entries
+_____________
+
+The following attributes are supported. Limits are read-write, reset_history
+is write-only and all the other attributes are read-only.
+
+======================= ==========================================
+in0_input		VP-VM voltage (mV).
+in0_min			Undervoltage threshold
+in0_max			Overvoltage threshold
+in0_lowest		Lowest measured voltage
+in0_highest		Highest measured voltage
+in0_reset_history	Write 1 to reset in1 history
+in0_min_alarm		Undervoltage alarm
+in0_max_alarm		Overvoltage alarm
+in0_label		Channel label (VP-VM)
+
+in1_input		DVCC voltage (mV)
+in1_min			Undervoltage threshold
+in1_max			Overvoltage threshold
+in1_lowest		Lowest measured voltage
+in1_highest		Highest measured voltage
+in1_reset_history	Write 1 to reset in2 history
+in1_min_alarm		Undervoltage alarm
+in1_max_alarm		Overvoltage alarm
+in1_label		Channel label (DVCC)
+
+curr1_input		IP-IM Sense current (mA)
+curr1_min		Undercurrent threshold
+curr1_max		Overcurrent threshold
+curr1_lowest		Lowest measured current
+curr1_highest		Highest measured current
+curr1_reset_history	Write 1 to reset curr1 history
+curr1_min_alarm		Undercurrent alarm
+curr1_max_alarm		Overcurrent alarm
+curr1_label		Channel label (IP-IM)
+
+power1_input		Power (in uW)
+power1_min		Low power threshold
+power1_max		High power threshold
+power1_input_lowest	Historical minimum power use
+power1_input_highest	Historical maximum power use
+power1_reset_history	Write 1 to reset power1 history
+power1_min_alarm	Low power alarm
+power1_max_alarm	High power alarm
+power1_label		Channel label (Power)
+
+temp1_input		Chip Temperature (in milliC)
+temp1_min		Low temperature threshold
+temp1_max		High temperature threshold
+temp1_input_lowest	Historical minimum temperature use
+temp1_input_highest	Historical maximum temperature use
+temp1_reset_history	Write 1 to reset temp1 history
+temp1_min_alarm		Low temperature alarm
+temp1_max_alarm		High temperature alarm
+temp1_label		Channel label (Ambient)
+
+temp2_min		Low temperature threshold for fan control
+temp2_max		High temperature threshold for fan control
+temp2_min_alarm		Low temperature fan control alarm
+temp2_max_alarm		High temperature fan control alarm
+temp2_label		Channel label (TEMPFAN)
+
+energy1_input		Measured energy over time (in microJoule)
+
+energy2_input		Measured energy over time (in microJoule)
+======================= ==========================================

MAINTAINERS

@@ -9630,6 +9630,16 @@ S:	Maintained
 F:	Documentation/hwmon/ltc4261.rst
 F:	drivers/hwmon/ltc4261.c
 
+LTC2947 HARDWARE MONITOR DRIVER
+M:	Nuno Sá <nuno.sa@analog.com>
+W:	http://ez.analog.com/community/linux-device-drivers
+L:	linux-hwmon@vger.kernel.org
+S:	Supported
+F:	drivers/hwmon/ltc2947-core.c
+F:	drivers/hwmon/ltc2947-spi.c
+F:	drivers/hwmon/ltc2947-i2c.c
+F:	drivers/hwmon/ltc2947.h
+
 LTC4306 I2C MULTIPLEXER DRIVER
 M:	Michael Hennerich <michael.hennerich@analog.com>
 W:	http://ez.analog.com/community/linux-device-drivers

drivers/hwmon/Kconfig

@@ -726,6 +726,33 @@ config SENSORS_LTC2945
 	  This driver can also be built as a module. If so, the module will
 	  be called ltc2945.
 
+config SENSORS_LTC2947
+	tristate
+
+config SENSORS_LTC2947_I2C
+	tristate "Analog Devices LTC2947 High Precision Power and Energy Monitor over I2C"
+	depends on I2C
+	select REGMAP_I2C
+	select SENSORS_LTC2947
+	help
+	  If you say yes here you get support for Linear Technology LTC2947
+	  I2C High Precision Power and Energy Monitor
+
+	  This driver can also be built as a module. If so, the module will
+	  be called ltc2947-i2c.
+
+config SENSORS_LTC2947_SPI
+	tristate "Analog Devices LTC2947 High Precision Power and Energy Monitor over SPI"
+	depends on SPI_MASTER
+	select REGMAP_SPI
+	select SENSORS_LTC2947
+	help
+	  If you say yes here you get support for Linear Technology LTC2947
+	  SPI High Precision Power and Energy Monitor
+
+	  This driver can also be built as a module. If so, the module will
+	  be called ltc2947-spi.
+
 config SENSORS_LTC2990
 	tristate "Linear Technology LTC2990"
 	depends on I2C

drivers/hwmon/Makefile

@@ -106,6 +106,9 @@ obj-$(CONFIG_SENSORS_LM95234)	+= lm95234.o
 obj-$(CONFIG_SENSORS_LM95241)	+= lm95241.o
 obj-$(CONFIG_SENSORS_LM95245)	+= lm95245.o
 obj-$(CONFIG_SENSORS_LTC2945)	+= ltc2945.o
+obj-$(CONFIG_SENSORS_LTC2947)	+= ltc2947-core.o
+obj-$(CONFIG_SENSORS_LTC2947_I2C) += ltc2947-i2c.o
+obj-$(CONFIG_SENSORS_LTC2947_SPI) += ltc2947-spi.o
 obj-$(CONFIG_SENSORS_LTC2990)	+= ltc2990.o
 obj-$(CONFIG_SENSORS_LTC4151)	+= ltc4151.o
 obj-$(CONFIG_SENSORS_LTC4215)	+= ltc4215.o